ARM: 7413/1: move read_{boot,persistent}_clock to the architecture level

At the moment, read_persistent_clock is implemented at the
platform level, which makes it impossible to compile these
platforms in a single kernel.

Implement these two functions at the architecture level, and
provide a thin registration interface for both read_boot_clock
and read_persistent_clock. The two affected platforms (OMAP and
Tegra) are converted at the same time.

Reported-by: Jeff Ohlstein <[e-mail]>
Tested-by: Stephen Warren <[e-mail]>
Tested-by: Tony Lindgren <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Signed-off-by: Russell King <[e-mail]>

arch/arm/include/asm/mach/time.h

···
 
 extern void timer_tick(void);
 
+struct timespec;
+typedef void (*clock_access_fn)(struct timespec *);
+extern int register_persistent_clock(clock_access_fn read_boot,
+				     clock_access_fn read_persistent);
+
 #endif

arch/arm/kernel/time.c

···
 }
 #endif
 
+static void dummy_clock_access(struct timespec *ts)
+{
+	ts->tv_sec = 0;
+	ts->tv_nsec = 0;
+}
+
+static clock_access_fn __read_persistent_clock = dummy_clock_access;
+static clock_access_fn __read_boot_clock = dummy_clock_access;;
+
+void read_persistent_clock(struct timespec *ts)
+{
+	__read_persistent_clock(ts);
+}
+
+void read_boot_clock(struct timespec *ts)
+{
+	__read_boot_clock(ts);
+}
+
+int __init register_persistent_clock(clock_access_fn read_boot,
+				     clock_access_fn read_persistent)
+{
+	/* Only allow the clockaccess functions to be registered once */
+	if (__read_persistent_clock == dummy_clock_access &&
+	    __read_boot_clock == dummy_clock_access) {
+		if (read_boot)
+			__read_boot_clock = read_boot;
+		if (read_persistent)
+			__read_persistent_clock = read_persistent;
+
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
 #if defined(CONFIG_PM) && !defined(CONFIG_GENERIC_CLOCKEVENTS)
 static int timer_suspend(void)
 {

arch/arm/mach-tegra/timer.c

···
 }
 
 /*
- * read_persistent_clock -  Return time from a persistent clock.
+ * tegra_read_persistent_clock -  Return time from a persistent clock.
  *
  * Reads the time from a source which isn't disabled during PM, the
  * 32k sync timer.  Convert the cycles elapsed since last read into
···
  * tegra_rtc driver could be executing to avoid race conditions
  * on the RTC shadow register
  */
-void read_persistent_clock(struct timespec *ts)
+static void tegra_read_persistent_clock(struct timespec *ts)
 {
 	u64 delta;
 	struct timespec *tsp = &persistent_ts;
···
 	tegra_clockevent.irq = tegra_timer_irq.irq;
 	clockevents_register_device(&tegra_clockevent);
 	tegra_twd_init();
+	register_persistent_clock(NULL, tegra_read_persistent_clock);
 }
 
 struct sys_timer tegra_timer = {

arch/arm/plat-omap/counter_32k.c

···
 #include <linux/io.h>
 #include <linux/clocksource.h>
 
+#include <asm/mach/time.h>
 #include <asm/sched_clock.h>
 
 #include <plat/hardware.h>
···
 }
 
 /**
- * read_persistent_clock -  Return time from a persistent clock.
+ * omap_read_persistent_clock -  Return time from a persistent clock.
  *
  * Reads the time from a source which isn't disabled during PM, the
  * 32k sync timer.  Convert the cycles elapsed since last read into
···
 static struct timespec persistent_ts;
 static cycles_t cycles, last_cycles;
 static unsigned int persistent_mult, persistent_shift;
-void read_persistent_clock(struct timespec *ts)
+static void omap_read_persistent_clock(struct timespec *ts)
 {
 	unsigned long long nsecs;
 	cycles_t delta;
···
 			printk(err, "32k_counter");
 
 		setup_sched_clock(omap_32k_read_sched_clock, 32, 32768);
+		register_persistent_clock(NULL, omap_read_persistent_clock);
 	}
 	return 0;
 }